The present invention relates to the handling of articles and, more particularly, relates to the handling of thin, flexible sheets of material by a vacuum apparatus.
In various production scenarios, it is necessary to handle thin, flexible sheets of material. Some of these thin, flexible sheets of material may be somewhat delicate so that special handling is required to avoid damaging these thin, flexible sheets of materials.
One particular type of a thin, flexible sheet of material is a so-called greensheet. The greensheet comprises ceramic material in a binder material. There may also be metallization on the greensheet in the form of wiring lines and vias. The binder material of the greensheet allows it to be handled and gives the greensheet a rubbery feel. However, while the greensheet is in the unsintered, i.e., green state, it must be delicately handled to avoid damaging the greensheet. And, when there is metallization on the greensheet, the greensheet can only be handled along the periphery of the greensheet.
Present day methods of handling greensheets include various devices which have vacuum cups or vacuum grooves around the device that enable the device to handle the greensheet. However, these devices cause edge damage and embossing of the greensheet, both of which are undesirable. Additionally, because of the spacing between vacuum cups, uneven handling of the greensheet often results.
While the present invention is directed to the handling of greensheets, it should be understood that the principles of the present invention have applicability to the handling of thin, flexible sheets of material in general.
Various proposals have been made for handling articles, including flexible sheets of material.
Baan et al. U.S. Pat. No. 5,971,454, the disclosure of which is incorporated by reference herein, discloses an article handler for picking up ceramic substrates by means of a vacuum. There is a plurality of compartments each of which is covered by a porous filter. The article handler is capable of picking up a variety of sizes of ceramic substrates.
Tsukushi U.S. Pat. No. 5,685,513, the disclosure of which is incorporated by reference herein, discloses a vacuum suction attachment pad wherein a pad body on a suction tool is designed to attach firmly to a smooth surface and wherein a plurality of suction ports are attached to a plenum that is attached to a vacuum source.
Croyle et al. U.S. Pat. No. 5,535,997, the disclosure of which is incorporated by reference herein, discloses a fabric piece automatic feeder with suction cup picker where a suction tool pad has a plurality of vacuum sources and vacuum ports attach to fabric flat pieces to transport them.
Lewecke et al. U.S. Pat. No. 4,703,966, the disclosure of which is incorporated by reference herein, discloses a vacuum lifting arrangement wherein a lift pad has a plenum with an attached piping to a vacuum and a plurality of vacuum ports, and an elastic sealing element in the form of a foam mat provided with a plurality of suction apertures.
In view of the efforts of others in this field, it is a purpose of the present invention to handle thin flexible sheets of material without causing damage to them.
It is another purpose of the present invention to handle thin flexible sheets of material by an apparatus which is lightweight and relatively inexpensive.
These and other purposes of the invention will become more apparent after referring to the following description of the invention considered in conjunction with the accompanying drawings.
The purposes of the invention have been achieved by providing a flexible sheet handling apparatus comprising:
a frame having a periphery;
at least one vacuum passage located around the periphery, the at least one vacuum passage having at least one outlet at the periphery;
at least one porous, polymeric plug covering the at least one outlet;
wherein when a vacuum is applied to the at least one vacuum passage, the at least one outlet and the at least one porous, polymeric plug, a flexible sheet in contact with the at least one porous, polymeric plug is uniformly held only around a periphery of the flexible sheet by the applied vacuum.